A model based control concept with knowledge based overhead control of a roasting process

Steelworks slag is used for the production of vanadium and, therefore, roasted under alkaline conditions in a rotary kiln or multiple hearth furnaces. This process is long known but the requirement for more efficient operation makes it difficult for the operator to handle the roaster in an optimal way manually. It is inevitable to hold a given process temperature profile and to provide the correct chemical environment for an efficient mode of operation and to avoid undesirable process states and critical conditions. This article contains a control concept for a multiple hearth roaster that enables a high degree of automation and is putting much emphasis on industrial applicability. The control concept comprises control loops for temperature control and control of chemical key values, the controller design is mainly based on a previously published dynamic model of the vanadium roast process. Since chemical analysis of the roasted media is considerably time consuming the Smith-predictor concept is utilized for improved control performance. Furthermore, a knowledge based supervising fuzzy controller is used to calculate the desired values in order to enhance process efficiency.